A pressure regulator is used to reduce a relatively high inlet pressure to a lower regulated pressure. Although the inlet pressure may vary, the regulated pressure should not vary substantially.
One use of a pressure regulator is to provide regulated water pressure for use in the water system of a recreational vehicle. Specifically, a source of water under pressure, such as a municipal water supply, is connected to the water system of the recreational vehicle through a pressure regulator. The pressures which the recreational vehicle water system may encounter in being coupled to various different water sources may vary widely. A primary purpose of the pressure regulator is to limit the pressure of the water introduced to the vehicle water system to a level which will not break or damage the fittings and other components of the water system.
A typical prior art regulator includes a housing defining an inlet chamber, a regulated pressure chamber and a closed chamber arranged in axially aligned relationship. A valve seat is located at the juncture of the inlet chamber and the regulated pressure chamber. A valve element lies partially in the inlet chamber and extends rearwardly through the regulated pressure chamber. The valve element is mounted on a movable diaphragm which divides the closed chamber from the regulated pressure chamber. A spring in the closed chamber acts against the diaphragm and urges the valve element toward an open position. The inlet pressure in the inlet chamber acts on the valve element, and the regulated pressure in the regulated pressure chamber acts on the diaphragm to urge the valve element toward a closed position. Thus, with this prior art construction, both the inlet pressure and the regulated pressure tend to close the valve element and only the spring tends to open the valve element.
One problem with this prior art construction is that it is subject to lock up. Lock up is a condition in which the valve element is locked in the closed position and no flow can occur through the pressure regulator. Lock up can occur, for example, if the inlet pressure materially increases when the valve element is in the closed position. In this event, the force of the spring may be insufficient to move the valve element to the open position even if the regulated pressure drops.
Another problem with this prior art pressure regulator is that its operation tends to be unstable and it may cause water hammer. For example, when the valve element closes, flow through the regulator is terminated. In this event, the pressure at the inlet of the regulator increases slightly because, at no flow, there are no line losses. This means that the regulated pressure must drop a predetermined significant increment before the force of the spring is sufficient to open the valve element. Similarly, as the valve element is moved toward the closed position and the pressure at the inlet rises slightly due to a reduction in line losses, this increase in inlet pressure augments the closing force already existing on the valve element. As a result, the valve element tends to accelerate toward the closed position, and the consequent abrupt shut off may produce water hammer.
Finally, this prior art pressure regulator has an inlet opening axially, and the regulated pressure outlet opens radially. This 90-degree relationship between the inlet and the outlet tends to create plumbing problems with installation in walls of different thicknesses. To overcome this, the prior art pressure regulator is designed in different size units because a single standard size would not meet all of the installation requirements.